Liquid crystal display device and manufacturing method for same

ABSTRACT

A liquid crystal display device with a higher aperture ratio is provided. According to one embodiment of the present invention, second color filters are formed so as to overlap with first color filters when adjacent color filters having different colors are formed on the TFT substrate side, so that the angle of the first tapers where said first color filters overlap and the angle of the second tapers where said second color filters overlap are set to 45° or more and 90° or less.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority over Japanese ApplicationsJP2009-145057 filed on Jun. 18, 2009 and JP2009-220215 filed on Sep. 25,2009, the contents of which are hereby incorporated into thisapplication by reference.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a liquid crystal display device and amanufacturing method for the same, and in particular, to a so-called COA(color-filter on array) liquid crystal display device where colorfilters are provided on the TFT substrate side, as well as amanufacturing method for the same.

(2) Description of the Related Art

Liquid crystal display devices (panels) have a pair of substrates thatare positioned so as to face each other and sandwich liquid crystal as ahousing, and thus are formed so that the light transmittance of theliquid crystal can be independently controlled in each pixel. Therefore,a number of pixels, which are units for color display, are each providedwith color filters of different colors, and these color filters areformed on the surface of the above described substrate that forms thehousing, on the liquid crystal side.

Signal lines which run between adjacent pixels, thin film transistorswhich are switching elements for selecting pixels, and pixel electrodesto which a video signal is supplied through a thin film transistor areformed on the surface of one of the substrates (in some cases referredto as TFT substrate), on the liquid crystal side of the pair ofsubstrates that form the housing of the liquid crystal display device.

Though the above described color filters are usually formed on thesubstrate that faces the above described TFT substrate (in some casesreferred to as facing substrate), in recent years color filters havecome to be provided also on the TFT substrate side.

JP2002-357828A, JP2003-050387A and JP2005-084231A all disclose a liquidcrystal display device where color filters are provided on the TFTsubstrate side. JP2002-357828A shows a configuration where color filtersof different colors provided on the two sides of the above describedsignal lines overlap above the signal lines (source lines), and thetable (Table 1) shows the width of the above described signal lines andthe angle of the taper at the overlapping end of the color filters.JP2003-050387A also shows a configuration where color filters ofdifferent colors provided on the two sides of the above described signallines overlap above the signal lines (source lines; in the figure thewidth is 40 μm), and the table (Table 1) also shows the width of theabove described signal lines and the angle of the taper at theoverlapping end of the color filters. JP2005-084231A also shows aconfiguration where color filters of different colors provided on thetwo sides of the above described signal lines overlap above the signallines. However, the width of the above described signal lines and theangle of the taper at the overlapping end of the color filters are notshown.

In addition, in liquid crystal display devices, at least a great numberof pixels are formed in a matrix so as to form a display region on thesurface of a pair of substrates positioned so as to face each other andsandwich liquid crystal, on the liquid crystal side. In addition, pixelelectrodes provided for each pixel, thin film transistors for selectingpixels, signal lines (gate signal lines) for driving these thin filmtransistors, and signal lines (drain signal lines) for supplying a videosignal to the pixel electrodes through the thin film transistors areformed on the surface of one substrate, on the liquid crystal side.

In liquid crystal display devices for color display, color filters madeof a resin material containing a pigment are usually formed on thesubstrate on which pixel electrodes and thin film transistors are notformed (TFT substrate), and these color filters allow three adjacentpixels to form a unit pixel for color display.

In recent years, however, color filters have come to be formed on thesubstrate on which pixel electrodes and thin film transistors areformed. This is the reason why this type of liquid crystal displaydevice is referred to as COA (color-filter on array). In this case,color filters are usually formed so as to cover thin film transistorsand work as a protective film for preventing the properties of the thinfilm transistors from deteriorating due to the direct contact with theliquid crystal.

In this case, pixel electrodes are electrodes for generating anelectrical field across the liquid crystal, and therefore formed in alayer above the color filters. Therefore, contact holes are usuallycreated in the color filters for electrical connection with the thinfilm transistors formed in a layer beneath the color filters.

JP2001-330851A and JP2000-29069A are examples of documents relating tothe present invention. JP2002-357828A describes a COA liquid crystaldisplay device where microscopic contact holes are created in the colorfilters in accordance with a laser irradiation method or a dry etchingmethod or through exposure to light or collective development. Inaddition, JP2003-050387A describes how a negative photosensitive resinfilm is formed of a color filter material on a light blocking film sothat contact holes can be created in the color filter through exposureto light from the rear and development using the light blocking film asa mask in a COA liquid crystal display device.

SUMMARY OF THE INVENTION

The liquid crystal display devices disclosed in the above JP2002-357828Aand JP2003-050387A, however, are both formed so that the angle of thetaper at the overlapping end of the color filters is small. In addition,though JP2005-084231A does not disclose the angle of the taper of thecolor filters, as described above, it also can be assumed to be small.

Thus, the width of the overlapping portion of the color filters may belarge in accordance with the small angle of the above described taper.In addition, the overlapping region of the color filters have arelatively large step, so that the alignment film formed on the surfacethat makes direct contact with the liquid crystal cannot be preventedfrom becoming abnormal in its alignment. Thus, portions with abnormalalignment are blocked from receiving light by making the width of thesignal lines in the lower layer large, for example, and as a result,pixel regions surrounded by the signal lines become narrow, and theaperture ratio of the pixels becomes smaller.

An object of the present invention is to provide a liquid crystaldisplay device with a higher aperture ratio.

In addition, it is preferable to make the diameter of the contact holescreated in the color filters smaller, in order to increase the apertureratio of the pixels in the COA liquid crystal display described above.In the case where the color filter layer made of a resin material isrelatively thick and diameter of the contact holes has to be smaller,however, it is desirable for the surface of the side walls of thecontact holes to be steep; that is to say, for the angle of the sidewalls to be wide relative to the surface of the substrate (angle oftaper of the contact holes).

Here, in a matrix of pixels, the color filters are red (R), blue (B) andgreen (G), for example, and color filters of the same color that coverpixels aligned in the direction y are aligned in such a manner that red(R), blue (B) and green (G) repeat in this order, for example, in thedirection x. In this case, adjacent color filters of different colorsoverlap along the ends, and it is desirable for the width of theoverlapping portion (amount of overlap of color) (color overlappingportion) and the height of the color overlapping portion (step of coloroverlap) to be small. This is because this makes the aperture ratio ofthe pixels is higher, the surface of the color filters flatter, and thealignment film more reliable.

In the case where the color filters are patterned together with thecreation of contact holes, as described above, in accordance withwell-known photolithographic technology, however, the surface of theside walls at the end of the color filters become steep; that is to say,the angle of the edge relative to the surface of the substrate (angle oftaper in the color overlapping portions) becomes wide when the angle ofthe taper in the contact holes is wider. As a result, the amount ofcolor overlap in the color overlapping portions and the step of coloroverlapping end up greater between adjacent color filters of differentcolors.

Another object of the present invention is to provide a COA liquidcrystal display device where the angle of the taper in the contact holesis wide and the angle of the taper in the color overlapping portions issmall, as well as a manufacturing method for the same.

The liquid crystal display device according to the present invention isformed so that the angle of the taper at the overlapping ends of thecolor filters is wide and the width of the signal lines in the layerbeneath the overlapping regions of the color filters is small.

The present invention can provide the following structures, for example.

(1) The liquid crystal display device according to the present inventionhas a pair of substrates that are positioned so as to face each otherand sandwich liquid crystal, wherein

gate signal lines made of a light blocking material which run in a firstdirection and are aligned in a second direction which crosses the abovedescribed first direction, and drain signal lines made of alightblocking material which run in the above described second direction andare aligned in the above described first direction, are formed on thesurface of one of the two substrates, on the liquid crystal side, and

thin film transistors which are turned on by a scanning signal through agate signal line and pixel electrodes to which a video signal issupplied from a drain signal line through a thin film transistor whenturned on are provided in pixel regions, pixel regions being defined asregions surrounded by two adjacent gate signal lines and two adjacentdrain signal lines, and is characterized in that

each of the above described pixel regions is provided with at least agate signal line, a drain signal line and a color filter formed in alayer above a thin film transistor,

overlapping regions between adjacent first color filters and secondcolor filters are provided in regions in which the above described drainsignal lines or the above described gate signal lines are formed asviewed from the top, and

the angle of the first taper of the above described first color filtersformed in the above described overlapping regions is set to 45° or moreand 90° or less relative to the surface of the above described drainsignal lines or gate signal lines, the angle of the second taper of theabove described second color filters formed in the above describedoverlapping regions is set to 45° or more and 90° or less relative tothe surface of the above described first color filters, and the width ofthe above described signal lines is set to 1 μm or more and 4 μm orless.

(2) The liquid crystal display device according to the present inventionis (1), characterized in that the film thickness of each color filter isset to 1 μm or more and 4 μm or less.

(3) The liquid crystal display device according to the present inventionis (1), characterized in that the film thickness of each color filter isset to 1 μm or more and 4 μm or less, and the overlapping portionsbetween the above described first color filters and the above describedsecond color filters have a step of 1 μm or less.

(4) The liquid crystal display device according to the present inventionis any of (1) to (3), characterized in that the end of the first taperof the above described first color filters overlaps with the secondtaper of the above described second color filters.

(5) The liquid crystal display device according to the present inventionis any of (1) to (4), characterized in that the angle of the first taperof the above described first color filters formed in the above describedoverlapping regions is set to 45° or more and 70° or less relative tothe surface of the above described drain signal lines or gate signallines, and the angle of the second taper of the above described secondcolor filters formed in the above described overlapping regions is setto 45° or more and 70° or less relative to the surface of the abovedescribed first color filters.

(6) The liquid crystal display device according to the present inventionis any of (1) to (5), characterized in that the density of the pigmentin the above described color filters is 10% or more and 60% or less.

(7) The liquid crystal display device according to the present inventionis any of (1) to (6), characterized in that the density of the pigmentin the above described second color filters is lower than the density ofthe pigment in the above described first color filters.

(8) The liquid crystal display device according to the present inventionis any of (1) to (7), characterized in that the relative dielectricconstant of the above described color filters is 3.0 or more and 7.0 orless.

(9) The liquid crystal display device according to the present inventionis any of (1) to 8, characterized in that the above described colorfilters are formed in accordance with a selective etching method bymeans of photolithographic technology using an aligner or stepper.

In addition, in accordance with the manufacturing method for a liquidcrystal display device according to the present invention, so-calledhalftone exposure to light is used for patterning COA color filters, sothat the angle of the tapers in the contact holes is wide and the angleof the taper in the color overlapping portions is small.

The present invention can provide the following structures, for example.

(10) The manufacturing method for a liquid crystal display deviceaccording to the present invention relates to a manufacturing method fora liquid crystal display device having: a pair of substrates provided soas to face each other and sandwich liquid crystal, gate signal lineswhich run in a first direction and are aligned in a second directionwhich crosses the above described first direction, and drain signallines which run the above described second direction and are aligned inthe above described first direction; thin film transistors driven by ascanning signal from a gate signal line; and color filters formed so asto cover the above described gate signal lines, the above describeddrain signal lines and the above described thin film transistors, andpixel electrodes formed in a layer above these color filters.

Furthermore, the manufacturing method for a liquid crystal displaydevice according to the present invention is characterized by comprisingthe steps of: forming the above described color filters with coloroverlapping portions where adjacent color filters having differentcolors overlap above said gate signal lines or drain signal lines asviewed from the top, and at the same time creating contact holes forelectrically connecting the above described pixel electrodes to theabove described thin film transistors; and carrying out halftoneexposure to light in the contact hole portion of each color filter,color overlapping portion, or both, so that the angle of the taper inthe above described color overlapping portion is smaller than the angleof the taper of the above described contact holes when the abovedescribed color filters are formed in accordance with photolithographictechnology.

(11) The manufacturing method for a liquid crystal display deviceaccording to the present invention is (10), characterized in that theangle of the taper in the above described color overlapping portions inthe above described color filters is 30° or more and 75° or less.

(12) The manufacturing method for a liquid crystal display deviceaccording to the present invention is (10), characterized in that theangle of the taper in the above described contact holes in the abovedescribed color filters is 45° or more and 90° or less.

(13) The manufacturing method for a liquid crystal display deviceaccording to the present invention is (10), characterized in that thecolor filters are formed so as too contain a pigment, and the density ofthe pigment is 10% or more and 60% or less.

(14) The manufacturing method for a liquid crystal display deviceaccording to the present invention is (10), characterized in that theamount of color overlap in the above described color overlappingportions in the above described color filter is 1 μm or more and 7 μM orless.

(15) The manufacturing method for a liquid crystal display deviceaccording to the present invention is (10), characterized in that thehalftone exposure to light in the above described color overlappingportions in the above described color filters is carried out in an area1 μm to 5 μm from the end of the above described color filters.

(16) The manufacturing method for a liquid crystal display deviceaccording to the present invention is (10), characterized in that thehalftone exposure to light in the above described contact portions inthe above described color filters is carried out in an area 1 μm to 5 μmfrom the edge of the above described contact portions.

(17) The liquid crystal display device according to the presentinvention has: a pair of substrates provided so as to face each otherand sandwich liquid crystal, gate signal lines which run in a firstdirection and are aligned in a second direction which crosses the abovedescribed first direction, and drain signal lines which run the abovedescribed second direction and are aligned in the above described firstdirection; thin film transistors driven by a scanning signal from a gatesignal line; and color filters formed so as to cover the above describedgate signal lines, the above described drain signal lines and the abovedescribed thin film transistors, and pixel electrodes formed in a layerabove these color filters.

Furthermore, the liquid crystal display device according to the presentinvention is characterized in that the above described color filtershave color overlapping portions where adjacent color filters havingdifferent colors overlap above the above described gate signal lines orthe above described drain signal lines as viewed from the top andcontact holes for electrically connecting the above described pixelelectrodes to the above described thin film transistors; and the angleof the taper in the above described color overlapping portion is smallerthan the angle of the taper of the above described contact holes.

(18) The liquid crystal display device according to the presentinvention is (17), characterized in that the angle of the taper in theabove described color overlapping portions in the above described colorfilters is 30° or more and 75° or less.

(19) The liquid crystal display device according to the presentinvention is (17), characterized in that the angle of the taper in theabove described contact holes in the above described color filters is45° or more and 90° or less.

(20) The liquid crystal display device according to the presentinvention is (17), characterized in that the color filters are formed soas too contain a pigment, and the density of the pigment is 10% or moreand 60% or less.

(21) The liquid crystal display device according to the presentinvention is (17), characterized in that the amount of color overlap inthe above described color overlapping portions in the above describedcolor filter is 1 μm or more and 7 μm or less.

Here, the above described structures are merely examples, and variousmodifications are possible for the present invention, as long as thetechnological idea is not deviated from. In addition, examples of thestructure of the present invention other than those described above willbecome clearer throughout the descriptions in the present specificationand the drawings.

In the above described Liquid crystal display device, it is possible toincrease the aperture ratio. In addition, in the above described liquidcrystal display device and according to the manufacturing method for thesame, the angle of the taper in the contact holes is wider and the angleof the taper in the color overlapping portions is smaller in the COAcolor filter.

Other effects of the present invention will become clearer throughoutthe descriptions in the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional diagram along line I-I in FIG. 2 showing theliquid crystal display device according to an embodiment of the presentinvention;

FIG. 2 is a plan diagram showing a pixel for the liquid crystal displaydevice according to one embodiment of the present invention;

FIG. 3 is a cross sectional diagram for illustrating the effects of theliquid crystal display device according to the present invention;

FIG. 4 is a cross sectional photograph showing a pixel of the liquidcrystal display device according to one embodiment of the presentinvention;

FIG. 5 is a diagram for illustrating the manufacturing method for acolor filter in the liquid crystal display device according to oneembodiment of the present invention;

FIG. 6 is a plan diagram showing a pixel of the liquid crystal displaydevice according to one embodiment of the present invention;

FIG. 7 is a cross sectional diagram along line in FIG. 2;

FIG. 8 is a cross sectional diagram along line IV-IV in FIG. 2;

FIG. 9 is a graph showing the angle of the taper in the coloroverlapping portions acquired for the amount of light for exposure fordifferent densities for the pigment contained in the color filters; and

FIG. 10 is a graph showing the color overlapping step for the angle ofthe taper in the color overlapping portions for different coloroverlapping amounts between adjacent color filters.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present invention are described below inreference to the drawings. Here, the same symbols are used forcomponents that are the same or similar in the drawings and embodiments,and descriptions that are the same are not repeated.

First Embodiment

The liquid crystal display device according to the present invention hasa pair of substrates that are positioned so as to face each other andsandwich liquid crystal, wherein gate signal lines made of a lightblocking material which run in a first direction and are aligned in asecond direction which crosses the above described first direction, anddrain signal lines made of alight blocking material which run in theabove described second direction and are aligned in the above describedfirst direction, are formed on the surface of one of the two substrates,on the liquid crystal side, and thin film transistors which are turnedon by a scanning signal through a gate signal line and pixel electrodesto which a video signal is supplied from a drain signal line through athin film transistor when turned on are provided in pixel regions, pixelregions being defined as regions surrounded by two adjacent gate signallines and two adjacent drain signal lines. Furthermore, each of theabove described pixel regions is provided with at least a gate signalline, a drain signal line and a color filter formed in a layer above athin film transistor. In addition, first color filters are provided soas to overlap with adjacent second color filters having a differentcolor so as not to protrude from the regions where the above describeddrain signal lines or gate signal lines are formed as viewed from thetop. First tapers are formed in the portions where the above describedfirst color filters overlap the above described second color filters.Second tapers are formed in the portions where the above describedsecond color filters are overlapped by the above described first colorfilters. The angle of the first taper is set to 45° or more and 90° orless relative to the surface of the above described drain signal linesor gate signal lines, the angle of the second taper of the abovedescribed second color filters formed in the above described overlappingregions is set to 45° or more and 90° or less relative to the surface ofthe above described first color filters, and the width of the abovedescribed signal lines is set to 1 μm or more and 4 μm or less.

<Structure of Pixels>

FIG. 2 is a plan diagram showing the structure of a pixel in the liquidcrystal display device according to the present invention, and theproduct for which the above described liquid crystal display device isused is of a 2.0 type VGA (400 ppi). The pixel shown in FIG. 2 is one ofa number of pixels aligned in a matrix. Thus, pixels having the samestructure are formed on the left, right, top and bottom of the pixel inthe figure. In addition, FIG. 1 shows a pixel formed on one of the twosubstrates positioned so as to face each other and sandwich liquidcrystal—namely, that referred to as TFT substrate. Here, FIG. 1 is across sectional diagram along line I-I in FIG. 2.

In FIG. 2, a semiconductor layer PS made of polysilicon, for example, isformed in island form on the surface of a substrate SUB1 (see FIG. 1).This semiconductor layer PS forms a semiconductor layer for a thin filmtransistor TFT and is patterned so as to be bent at the center and haveportions with a large area at both ends. Here, the thin film transistorTFT is an MIS (metal insulator semiconductor) transistor having aso-called top gate structure where the gate electrode is formed in alayer above the semiconductor layer PS, as described below.

An insulating film GI (see FIG. 1) is formed so as to cover thesemiconductor layer PS on the surface of the substrate SUB1. Thisinsulating film GI works as a gate insulating film for the abovedescribed thin film transistor TFT in the region where the thin filmtransistor TFT is formed.

Gate signal lines GL which run in the direction x in the figure and arealigned in the direction y are formed on the surface of the insulatingfilm GI. These gate signal lines GL are formed of a light blockingmaterial. These gate signal lines GL are formed so as to run betweenpixels aligned in the direction y in the figure. In addition, the gatesignal lines GL are formed so as to cross one point on the abovedescribed semiconductor layer PS, and at the same time have a protrusionwhich crosses another point on the above described semiconductor layerPS (indicated by the symbol GLpj in the figure). As a result, the gatesignal lines GL work as a gate electrode for the thin film transistorTFT at the point where they cross the semiconductor layer PS (doublegate). Here, in the semiconductor layer PS, the channel region for thethin film transistor TFT is formed in the region directly beneath theabove described gate electrode when an impurity is injected using theabove described gate electrode as a mask, after the formation of thegate signal lines GL.

An interlayer insulating film IN1 (see FIG. 1) is formed so as to coverthe gate signal lines GL on the surface of the insulating film GI, anddrain signal lines DL which run in the direction y in the figure and arealigned in the direction x are formed on the upper surface of thisinterlayer insulating film IN1. These drain signal lines DL are formedof a light blocking material. The drain signal lines DL are formed so asto run between pixels aligned in the direction x in the figure. Here,the width W of the drain signal lines DL is very small—for example 3μm—in comparison with the prior art. This is in order to increase thearea of the pixels and the aperture ratio of the pixels. The drainsignal lines DL are formed above the region where one end of the abovedescribed semiconductor layer PS has a large area, and electricallyconnected to one end of the above described semiconductor layer PSthrough a through hole TH1 created in the interlayer insulating film IN1in advance. The portions of the drain signal lines DL that areelectrically connected to the semiconductor layer PS work as the drainelectrode DT of a thin film transistor TFT.

In addition, the source electrode ST of the thin film transistor TFT isformed above the region where the other end of the above describedsemiconductor layer PS has a large area when the drain signal lines DLare formed, and this source electrode ST is electrically connected tothe above described end of the semiconductor layer PS through a throughhole TH2 created in the interlayer insulating film IN1 in advance. Thissource electrode ST is connected to the below described pixel electrodePX.

A passivation film PAS (see FIG. 1) is formed on the surface of theinterlayer insulating film IN1 on which the drain signal lines DL (drainelectrodes DT) and the source electrodes ST of the thin film transistorsTFT are formed, as described above, so as to cover the drain signallines DL (drain electrodes DT) and the source electrodes ST. Thispassivation film PAS is formed so as to prevent the thin filmtransistors TFT from making contact with the liquid crystal, forexample, and has a two-layer structure of an inorganic insulating filmPAS1 (see FIG. 1) and an organic insulating film PAS 2 (see FIG. 1), forexample.

Here, the organic insulating film PAS 2 is formed of a resin material,for example, and also works as a color filter CF. The color filters CFhave the same color in pixel groups of pixels aligned in the direction yin FIG. 2, for example, and are patterned in strips covering the abovedescribed pixels. Thus, blue (B) color filters CF (indicated by thesymbol CF(B) in the figure), red (R) color filters CF (indicated by thesymbol CF(R) in the figure), and green (G) color filters CF (indicatedby the symbol CF(G) in the figure) patterned in strips, as describedabove, are aligned so as to repeat in this order in the direction x inthe figure. The pixel in FIG. 2 forms a unit pixel for color displaytogether with the pixels to its left and right. The color filter CF(R)in FIG. 2 has a portion (color overlapping portion) that overlaps thecolor filter CF(B) to its left above the drain signal line DL (indicatedby the symbol DL (DL1) in the figure), and a portion (color overlappingportion) that overlaps the color filter CF(G) to its right above thedrain signal line DL (indicated by the symbol DL (DLr) in the figure).The structure of this color filter CF is described in detail below.

A counter electrode CT made of a transparent conductive film, such as ofITO (indium tin oxide) is formed on the top surface of the color filterCF, which also works as a passivation film PAS 2. This counter electrodeCT is formed as a flat electrode which almost completely covers eachpixel, and crosses the drain signal line DL so as to be shared by pixelsaligned in the direction x in the figure. A reference signal thatbecomes a reference for a video signal is supplied to this counterelectrode CT from outside the display region.

An interlayer insulating film IN2 (see FIG. 1) is formed on the surfaceon which the counter electrode CT is formed so as to cover the abovedescribed counter electrode CT, and a pixel electrode PX made of ITO,for example, is formed for each pixel on the surface of this interlayerinsulating film IN2. The pixel electrode PX is formed of a number oflines (two in the figure) which run in the direction y in the figure andare aligned in the direction x, for example. In addition, theseelectrodes are patterned so as to be connected to each other at the endson the same side. This is in order to keep the number of electrodes atthe same potential. In addition, the pixel electrode PX is electricallyconnected to the source electrode ST of the thin film transistor TFTthrough a through hole TH3 that is created in the interlayer insulatingfilm IN2, the passivation film PAS2 (color filter CF) and thepassivation film PAS1 in advance at the end on the thin film transistorTFT side.

Though not shown in FIG. 1, an alignment film is formed on theinterlayer insulating film IN2 so as to cover the pixel electrode PX,and this alignment film makes direct contact with the liquid crystal, sothat the direction in which liquid crystal molecules are initiallyaligned can be determined.

<Structure of Color Filters CF>

As shown in FIG. 1, color filters CF include first color filters, secondcolor filters and third color filters. In the case of this, firstembodiment, the first color filters are blue filters CF(B), the secondcolor filters are red filters CF(R) and the third color filters aregreen filters CF(G). The color filters CF are formed in the order ofblue (B), red (R) and green (G). These color filters CF all have a filmthickness of 2.0 μm. In this case, color filters CF of different colorsare provided so as to overlap above the drain signal lines DL.

In FIG. 1, DLr is a drain signal line for sending a data signal to a redpixel, and DLg is a drain signal line for sending a data signal to agreen pixel.

The red filter CF(R) overlaps the blue filter CF(B) above the red drainsignal line DLr. The green filter CF(G) overlaps the red filter CF(R)above the green drain signal line DLg. Though not shown in FIG. 1, thegreen filter CF(G) overlaps the blue filter CF(B) above the blue drainsignal line. In the image display region, these color filters fordifferent colors are aligned so as to repeat. In addition, tapers havingan angle θ1 as viewed in a cross section are formed at the two ends ofthe first color filters. A taper having an angle θ21 as viewed in across section is formed at the one end of the second color filters inthe portion where they overlap with the first color filters, and a taperhaving an angle θ22 as viewed in a cross section is formed at the otherend of the second color filters. A taper having an angle θ31 as viewedin a cross section is formed at the one end of the third color filtersin the portion where they overlap with the second color filters, and thetaper in the portion where the third color filter overlaps the firstcolor filter as viewed in a cross section is formed at the other end ofthe third color filters. The overlapping portions between the colorfilters are formed in regions which are narrower than the width of thedrain signal lines.

Here, though the overlapping regions are located above the drain signallines in the present embodiment, the same structure may be used in thecase where the overlapping regions are located above the gate signallines.

The blue filter CF(B) is formed so that the end does not protrude fromthe end of the above described drain signal line DLr on the pixel sidewhere the red filter CF(R) is formed, and a taper having an angle θ1 (of45)° relative to the surface of the above described drain signal lineDLr is formed (the above described angle θ1 is in some cases referred toas angle of the taper). In order to gain the angle θ1 of the taperdescribed above in the blue filter CF(B), selective etching usingphotolithographic technology may be carried out on a resin materialcontaining 30% of a blue pigment. That is to say, the angle θ1 of thetaper can be controlled by means of the pigment content.

The red filter CF(R) is formed so that the end does not protrude fromthe end of the above described drain signal line DL1 on the pixel sidewhere the blue filter CF(B) is formed. Furthermore, the angle θ21 of thetaper of the red filter is set to 50° relative to the surface of theabove described first color filter (the above described angle θ21 is insome cases referred to as angle of the taper). In order to gain theangle θ21 of the taper described above in the red filter CF(R),selective etching using photolithographic technology may be carried outon a resin material containing 30% or a red pigment. In this case, thephotolithographic technology makes high-precision processing possible,if a method using an aligner or a stepper is adopted. The other end ofthe red filter CF(R) is formed on the drain signal line (indicated bythe symbol DLg in the figure) adjacent to the above described drainsignal line DLr. A taper having an angle θ22 (of 50°) relative to thesurface of the above described drain signal line DLr is formed so as notto protrude from the end of the above described drain signal line DLr onthe pixel side where the green filter CF(G) is formed.

The green filter CFR(g) is formed so that the end does not protrude fromthe end of the above described drain signal line DL1 on the pixel sidewhere the color filter CF(R) is formed. In addition, a taper having anangle θ3 (of 60°) relative to the surface of the above described drainsignal line DLg is formed (the above described angle θ3 is in some casesreferred to as angle of the taper). In order to gain the above describedangle θ3 of the taper in the green filter CF(G), selective etching usingphotolithographic technology may be carried out on a resin materialcontaining 405 of a blue pigment.

The thus formed color filters CF have relatively large taper anglesformed at their ends, so that the region for the overlapping portions(overlapping region) is relatively narrow when adjacent color filters CFhaving different colors are formed so as to overlap. Thus, theoverlapping region can be contained within the region of the width W (3μm) of the drain signal lines DL. As a result, the width of the drainsignal lines DL can be narrowed to the above described value, so thatthe aperture ratio of the pixels can be increased.

Here, in the case of the above described configuration, the differencein thickness between the color filters CF having different colors andtheir overlapping portions can be confirmed to be smaller. FIG. 3 is adiagram showing overlapping color filters CF(B), CF(R), CF(G) and CF(B)aligned in this order from the left. As shown in FIG. 3, the differencein thickness DL1 between the color filter CF(B) and the portion of thecolor filter CF(R) that overlaps the color filter CF(B) is 0.4 μm, thedifference in thickness DL2 between the color filter CF(B) and theportion of the color filter CF(G) that overlaps the color filter CF(B)is 0.6 μm, and the difference in thickness DL3 between the color filterCF(R) and the portion of the color filter CF(G) that overlaps the colorfilter CF(R) is 0.8 μm. The difference is much smaller than in the priorart, and the area of the alignment film formed on the surface that makesdirect contact with the liquid crystal, where the alignment is abnormal,can be contained within the width W of the above described drain signallines DL (3 μm). In addition, in FIGS. 2 and 3, the end of the colorfilters in the upper layer extends to the flat portion of the colorfilters in the lower layer (surface parallel to the upper surface of thesignal wires).

Here, the product for which the invention is used, the width of the TFTwires (width of drain signal lines DL), the aperture ratio (apertureratio of pixels), the order in which G, R and B are layered (the orderin which color filters of different colors are layered), the GRBproperties (properties of the color filters having different colors, andthe difference in thickness between each color filter and theiroverlapping portions in the configuration in the above described firstembodiment appear in this order in the row corresponding to the firstembodiment in the following Table 1.

TABLE 1 Embodiments of Present Invention Difference in thickness ProductOrder GRB properties between color filters for which Width in which FilmRelative Angle and overlapping portions invention of TFT Aperture GRBare Pigment thick- dielectric of Dif- Embodiment is used wires ratiolayered Color density ness constant taper Location ference Comparative2.0 type VGA 12 μm  33% G→R→B G 40% 2.0 μm 3.7 10° Portion R overlappingG 1.2 μm Example 1 (400 ppi) R 30% 2.0 μm 3.5 10° Portion B overlappingG 1.2 μm B 30% 2.0 μm 3.6 10° Portion B overlapping R 1.2 μm First 2.0type VGA 3 μm 65% B→R→G G 40% 2.0 μm 3.7 60° Portion R overlapping B 0.4μm Embodiment (400 ppi) R 30% 2.0 μm 3.5 50° Portion G overlapping B 0.6μm B 30% 2.0 μm 3.6 45° Portion G overlapping R 0.8 μm Second 2.0 typeVGA 4 μm 62% G→R→B G 20% 4.0 μm 3.6 45° Portion R overlapping G 0.2 μmEmbodiment (400 ppi) R 10% 4.0 μm 3.0 45° Portion B overlapping G 0.2 μmB 10% 4.0 μm 3.3 45° Portion B overlapping R 0.2 μm Third 2.0 type VGA 2μm 69% B→R→G G 60% 1.0 μm 7.0 90° Portion R overlapping B 0.4 μmEmbodiment (400 ppi) R 50% 1.0 μm 6.0 80° Portion G overlapping B 0.6 μmB 40% 1.0 μm 5.0 70° Portion G overlapping R 0.8 μm Fourth 2.0 type VGA2 μm 69% G→R→B G 50% 1.0 μm 7.0 90° Portion R overlapping G 1.0 μmEmbodiment (400 ppi) R 40% 1.0 μm 6.0 80° Portion B overlapping G 0.8 μmB 40% 1.0 μm 5.0 70° Portion B overlapping R 0.6 μm Fifth 4.0 type QVGA3 μm 91% R→G→B G 30% 3.0 μm 4.0 50° Portion G overlapping R 0.4 μmEmbodiment (100 ppi) R 30% 2.8 μm 4.0 55° Portion B overlapping R 0.5 μmB 30% 2.6 μm 4.0 60° Portion B overlapping G 0.6 μm Sixth 2.0 type VGA 4μm 62% G→R→B G 20% 1.0 μm 3.9 60° Portion R overlapping G 0.4 μmEmbodiment (400 ppi) R 10% 1.0 μm 3.3 60° Portion B overlapping G 0.4 μmB 10% 1.0 μm 3.6 60° Portion B overlapping R 0.4 μm Seventh 2.0 type VGA2 μm 69% B→R→G G 60% 4.0 μm 6.0 80° Portion R overlapping B 0.3 μmEmbodiment (400 ppi) R 50% 4.0 μm 5.0 70° Portion G overlapping B 0.5 μmB 40% 4.0 μm 4.0 60° Portion G overlapping R 0.7 μm

That is to say, as shown in FIG. 2, the order in which color filters CFof different colors are formed is CF(B), CF(R) and CF(G). In this case,the color filters CF(G) have a relative dielectric constant of 3.7 andthe angle θ3 of the taper at the end is 60° when the density of thepigment is 40% and the film thickness is 2.0 μm, the color filters CF(R)have a relative dielectric constant of 3.5 and the angle θ2 of the taperat the end is 50° when the density of the pigment is 30% and the filmthickness is 2.0 μm, and the color filters CF(B) have a relativedielectric constant of 3.6 and the angle θ1 of the taper at the end is50° when the density of the pigment is 30% and the film thickness is 2.0μm. In addition, the difference in thickness between the color filtersCF(B) and the color filters CF(R) overlapping the color filters CF(B) is0.4 μm, the difference in thickness between the color filters CF(B) andthe color filters CF(G) overlapping the color filters CF(B) is 0.6 μm,and the difference in thickness between the color filters CF(R) and thecolor filters CF(G) overlapping the color filters CF(R) is 0.8 μm. Thus,the aperture ratio of pixels is as high as 65%.

In addition, the end of the color filter in the upper layer in FIG. 4 isover the taper of the color filter in the lower layer. In the case ofthis configuration also, the angle θ1 of the first taper of the firstcolor filter formed in the overlapping region is set to 45° or more and90° or less relative to the surface of the drain signal line or gatesignal line, while the angle θ2 of the second taper of the second colorfilter formed in the overlapping region is set to 45° or more and 90° orless relative to the surface of the first color filter, and the width ofthe signal lines is set to 1 μm or more and 4 μm or less.

In this configuration, the overlapping regions between adjacent firstand second color filters are located within the regions where the drainsignal lines and the gate signal lines are formed as viewed from thetop.

Second Embodiment

The second embodiment onward have more or less the structure shown inFIGS. 1 to 3, and therefore, the following descriptions are also basedon Table 1.

The product for which the invention is used is the same as in the firstembodiment. The order in which color filters CF for each pixel arelayered in unit pixels is green (G), red (R) and blue (B). In thefollowing descriptions, green is simply referred to as G, red is simplyreferred to as R, and blue is simply referred to as B for the sake ofsimplicity.

The density of the pigment in the color filters G is 20%, the filmthickness is 4.0 μm, the relative dielectric constant is 3.6, and theangle of the taper is 45°. The density of the pigment in the colorfilters R is 10%, the film thickness is 4.0 μm, the relative dielectricconstant is 3.0, and the angle of the taper is 45°. The density of thepigment in the color filters B is 10%, the film thickness is 4.0 μm, therelative dielectric constant is 3.3, and the angle of the taper is 45°.The difference in thickness between the color filters for G and thecolor filters for R overlapping the color filters for G is 0.2 μm, thedifference in thickness between the color filters for G and the colorfilters for B overlapping the color filters for G is 0.2 μm, and thedifference in thickness between the color filters for R and the colorfilters for B overlapping the color filters for R is 0.2 μm. As aresult, the wires are as narrow as 4 μm, and the aperture ratio of thepixels is as high as 62%.

Third Embodiment

The product for which the invention is used is the same as in the firstembodiment. The order in which color filters for each pixel are layeredin unit pixels is B, R and G.

The density of the pigment in the color filters B is 40%, the filmthickness is 1.0 μm, the relative dielectric constant is 5.0, and theangle of the taper is 70°. The density of the pigment in the colorfilters R is 50%, the film thickness is 1.0 μm, the relative dielectricconstant is 6.0, and the angle of the taper is 80°. The density of thepigment in the color filters G is 60%, the film thickness is 1.0 μm, therelative dielectric constant is 7.0, and the angle of the taper is 90°.The difference in thickness between the color filters for B and thecolor filters for R overlapping the color filters for B is 0.4 μm, thedifference in thickness between the color filters for B and the colorfilters for G overlapping the color filters for B is 0.6 μm, and thedifference in thickness between the color filters for R and the colorfilters for G overlapping the color filters for R is 0.8 μm. As aresult, the wires are as narrow as 2 μm, and the aperture ratio of thepixels is as high as 69%.

Here, in the case of this, third embodiment, the density of the pigmentin the color filters in the lower layer in the overlapping portions issmaller than the density of the pigment in the color filters in theupper layer (it may be the same in the case where the density of thepigment is as in the following fourth embodiment). In this case, theangle of the taper is small when the density of the pigment is small,and therefore, the lower layer has a small taper angle. Thus, as isclear from Table 1, the difference in thickness between color filtersand their overlapping portions can be made smaller.

Fourth Embodiment

The product for which the invention is used is the same as in the firstembodiment. The order in which color filters for each pixel are layeredin unit pixels is G, R and B.

The density of the pigment in the color filters G is 50%, the filmthickness is 1.0 μm, the relative dielectric constant is 7.0, and theangle of the taper is 90°. The density of the pigment in the colorfilters R is 40%, the film thickness is 1.0 μm, the relative dielectricconstant is 6.0, and the angle of the taper is 80°. The density of thepigment in the color filters B is 40%, the film thickness is 1.0 μm, therelative dielectric constant is 5.0, and the angle of the taper is 70°.The difference in thickness between the color filters for G and thecolor filters for R overlapping the color filters for G is 1.0 μm, thedifference in thickness between the color filters for G and the colorfilters for B overlapping the color filters for G is 0.8 μm, and thedifference in thickness between the color filters for R and the colorfilters for B overlapping the color filters for R is 0.6 μm. As aresult, the wires are as narrow as 2 μm, and the aperture ratio of thepixels is as high as 69%.

Fifth Embodiment

The product for which the invention is used is a 4.0 type QVGA (100ppi). The order in which color filters for each pixel are layered inunit pixels is R, G and B.

The density of the pigment in the color filters R is 30%, the filmthickness is 2.8 μm, the relative dielectric constant is 4.0, and theangle of the taper is 55°. The density of the pigment in the colorfilters G is 30%, the film thickness is 3.0 μm, the relative dielectricconstant is 4.0, and the angle of the taper is 50°. The density of thepigment in the color filters B is 30%, the film thickness is 2.6 μm, therelative dielectric constant is 4.0, and the angle of the taper is 60°.The difference in thickness between the color filters for R and thecolor filters for G overlapping the color filters for R is 0.4 μm, thedifference in thickness between the color filters for R and the colorfilters for B overlapping the color filters for R is 0.5 μm, and thedifference in thickness between the color filters for G and the colorfilters for B overlapping the color filters for G is 0.6 μm. As aresult, the wires are as narrow as 3 μm, and the aperture ratio of thepixels is as high as 91%.

Sixth Embodiment

The product for which the invention is used is the same as in the firstembodiment. The order in which color filters for each pixel are layeredin unit pixels is G, R and B.

The density of the pigment in the color filters G is 20%, the filmthickness is 1.0 μm, the relative dielectric constant is 3.9, and theangle of the taper is 60°. The density of the pigment in the colorfilters R is 10%, the film thickness is 1.0 μm, the relative dielectricconstant is 3.3, and the angle of the taper is 60°. The density of thepigment in the color filters B is 10%, the film thickness is 1.0 μm, therelative dielectric constant is 3.6, and the angle of the taper is 60°.The difference in thickness between the color filters for G and thecolor filters for R overlapping the color filters for G is 0.4 μm, thedifference in thickness between the color filters for G and the colorfilters for B overlapping the color filters for G is 0.4 μm, and thedifference in thickness between the color filters for R and the colorfilters for B overlapping the color filters for R is 0.4 μm. As aresult, the wires are as narrow as 4 μm, and the aperture ratio of thepixels is as high as 62%.

Seventh Embodiment

The product for which the invention is used is the same as in the firstembodiment. The order in which color filters for each pixel are layeredin unit pixels is B, R and G.

The density of the pigment in the color filters B is 40%, the filmthickness is 4.0 μm, the relative dielectric constant is 4.0, and theangle of the taper is 60°. The density of the pigment in the colorfilters R is 50%, the film thickness is 4.0 μm, the relative dielectricconstant is 5.0, and the angle of the taper is 70°. The density of thepigment in the color filters G is 60%, the film thickness is 4.0 μm, therelative dielectric constant is 6.0, and the angle of the taper is 80°.The difference in thickness between the color filters for B and thecolor filters for R overlapping the color filters for B is 0.3 μm, thedifference in thickness between the color filters for B and the colorfilters for G overlapping the color filters for B is 0.5 μm, and thedifference in thickness between the color filters for R and the colorfilters for G overlapping the color filters for R is 0.7 μm. As aresult, the wires are as narrow as 2 μm, and the aperture ratio of thepixels is as high as 69%.

Comparative Example 1

The product for which the invention is used is the same as in the firstembodiment. The order in which color filters for each pixel are layeredin unit pixels is G, R and B.

The density of the pigment in the color filters G is 40%, the filmthickness is 2.0 μm, the relative dielectric constant is 3.7, and theangle of the taper is 10°. The density of the pigment in the colorfilters R is 30%, the film thickness is 2.0 μm, the relative dielectricconstant is 3.5, and the angle of the taper is 10°. The density of thepigment in the color filters B is 30%, the film thickness is 2.0 μm, therelative dielectric constant is 3.6, and the angle of the taper is 10°.The difference in thickness between the color filters for G and thecolor filters for R overlapping the color filters for G is 1.2 μm, thedifference in thickness between the color filters for G and the colorfilters for B overlapping the color filters for G is 1.2 μm, and thedifference in thickness between the color filters for R and the colorfilters for B overlapping the color filters for R is 1.2 μm. As aresult, the wires are as wide as 12 μm, and the aperture ratio of thepixels is as low as 33%.

Eighth Embodiment

In the above described embodiments, the portions where color filters ofdifferent colors overlap are located above drain signal lines DL.However, the invention is not limited to this, and the overlappingportions may be located above gate signal lines GL. Thus, the inventioncan be applied in portions above the gate signal lines GL.

Ninth Embodiment

In the above described embodiments, IPS (in-plane switching) liquidcrystal display devices are described. However, the invention is notlimited to this, and can be applied to TN (twisted nematic) or VA(vertical alignment) liquid crystal display devices, for example.

Tenth Embodiment

In the following, the tenth to twenty-eighth embodiments of the presentinvention and Comparative Examples 2 to 6 which relate to these aredescried in reference to the drawings. Here, the same symbols are usedfor components that are the same or similar in the drawings and theembodiments, and descriptions that are the same are not repeated.

<Structure of Pixels>

FIG. 6 is a plan diagram showing a pixel of the liquid crystal displaydevice according to one embodiment of the present invention. The pixelin FIG. 6 is one of a number of pixels aligned in a matrix. Thus, pixelshaving the same structure are formed on the left, right, top and bottomof the pixel in the figure. In addition, FIG. 7 is a cross sectionaldiagram along line in FIG. 6, and FIG. 8 is a cross sectional diagramalong line IV-IV in FIG. 6. FIGS. 7 and 8 both show a pixel formed onone of the two substrates positioned so as to face each other andsandwich liquid crystal—namely, that referred to as TFT substrate.

In FIG. 6, a semiconductor layer PS made of polysilicon, for example, isformed in island form on the surface of a substrate SUB1 (see FIGS. 7and 8). This semiconductor layer PS forms a semiconductor layer for athin film transistor TFT and is patterned so as to be bent at the centerand have portions with a large area at both ends. Here, the thin filmtransistor TFT is an MIS (metal insulator semiconductor) transistorhaving a so-called top gate structure where the gate electrode is formedin a layer above the semiconductor layer PS, as described below.

An insulating film GI (see FIGS. 7 and 8) is formed so as to cover thesemiconductor layer PS on the surface of the substrate SUB1. Thisinsulating film GI works as a gate insulating film for the abovedescribed thin film transistor TFT in the region where the thin filmtransistor TFT is formed.

Gate signal lines GL which run in the direction x in the figure and arealigned in the direction y are formed on the surface of the insulatingfilm GI. These gate signal lines GL are formed so as to run betweenpixels aligned in the direction y in the figure. In addition, the gatesignal lines GL are formed so as to cross one point on the abovedescribed semiconductor layer PS, and at the same time have a protrusionwhich crosses another point on the above described semiconductor layerPS (indicated by the symbol GLpj in the figure). As a result, the gatesignal lines GL work as a gate electrode for the thin film transistorTFT at the point where they cross the semiconductor layer PS (doublegate). Here, in the semiconductor layer PS, the channel region for thethin film transistor TFT is formed in the region directly beneath theabove described gate electrode when an impurity is injected using theabove described gate electrode as a mask, after the formation of thegate signal lines GL.

An interlayer insulating film IN1 (see FIGS. 7 and 8) is formed so as tocover the gate signal lines GL on the surface of the insulating film GI,and drain signal lines DL which run in the direction y in the figure andare aligned in the direction x are formed on the upper surface of thisinterlayer insulating film IN1. These drain signal lines DL are formedso as to run between pixels aligned in the direction x in the figure.The drain signal lines DL are formed above the region where one end ofthe above described semiconductor layer PS has a large area, andelectrically connected to one end of the above described semiconductorlayer PS through a through hole TH1 created in the interlayer insulatingfilm IN1 in advance. The portions of the drain signal lines DL that areelectrically connected to the semiconductor layer PS work as the drainelectrode DT of a thin film transistor TFT.

In addition, the source electrode ST of the thin film transistor TFT isformed above the region where the other end of the above describedsemiconductor layer PS has a large area when the drain signal lines DLare formed, and this source electrode ST is electrically connected tothe above described end of the semiconductor layer PS through a throughhole TH2 created in the interlayer insulating film IN1 in advance. Thissource electrode ST has a relatively large area in its extending portionand is connected to the below described pixel electrode PX in thisportion.

A passivation film PAS (see FIGS. 7 and 8) is formed on the surface ofthe interlayer insulating film IN1 on which the drain electrodes (drainsignal lines DL) and the source electrodes ST of the thin filmtransistors TFT are formed, as described above, so as to cover the drainsignal lines DL and the source electrodes ST. This passivation film PASis formed so as to prevent the thin film transistors TFT from makingcontact with the liquid crystal, for example, and has a two-layerstructure where an inorganic insulating film PAS1 (see FIGS. 7 and 8)and an organic insulating film PAS 2 (see FIGS. 7 and 8) are layered insequence, for example.

Here, the organic insulating film PAS 2 is formed of a resin material,for example, and also works as a color filter CF. That is to say, theorganic insulating film PAS is made of a resin material containing apigment of a predetermined color. The color filters CF have the samecolor in pixel groups of pixels aligned in the direction y in FIG. 6,for example, and are patterned in strips covering the above describedpixels. Thus, blue (B) color filters CF (indicated by the symbol CF(B)in the figure), red (R) color filters CF (indicated by the symbol CF(R)in the figure), and green (G) color filters CF (indicated by the symbolCF(G) in the figure) patterned in strips, as described above, arealigned so as to repeat in this order in the direction x in the figure.The pixel in FIG. 6 forms a unit pixel for color display together withthe pixels to its left and right. The color filter CF(R) in FIG. 6 has aportion (color overlapping portion) that overlaps the color filter CF(B)to its left above the drain signal line DL (indicated by the symbol DL(DL1) in the figure), and a portion (color overlapping portion) thatoverlaps the color filter CF(G) to its right above the drain signal lineDL (indicated by the symbol DL (DLr) in the figure). The structure ofthis color filter CF is described in detail below.

A counter electrode CT made of a transparent conductive film, such as ofITO (indium tin oxide) is formed on the top surface of the color filterCF, which also works as a passivation film PAS 2. This counter electrodeCT is formed as a flat electrode which almost completely covers eachpixel, and crosses the drain signal line DL so as to be shared by pixelsaligned in the direction x in the figure. A reference signal thatbecomes a reference for a video signal is supplied to this counterelectrode CT from outside the display region. Here, an opening OP iscreated in the counter electrode CT in the vicinity of the thin filmtransistor TFT. As described below, the source electrode ST of the abovedescribed thin film transistor TFT is electrically connected to thebelow described pixel electrode PX in this portion, which is provided inorder to prevent the electrical connection portion from short-circuitingwith the counter electrode CT.

An interlayer insulating film IN2 (see FIGS. 7 and 8) is formed on thesurface on which the counter electrode CT is formed so as to cover theabove described counter electrode CT, and a pixel electrode PX made ofITO, for example, is formed for each pixel on the surface of thisinterlayer insulating film IN2. The pixel electrode PX is formed of anumber of lines (two in the figure) which run in the direction y in thefigure and are aligned in the direction x, for example. In addition,these electrodes are patterned so as to be connected to each other atthe ends on the same side. This is in order to keep the number ofelectrodes at the same potential. In addition, the pixel electrode PX iselectrically connected to the source electrode ST of the thin filmtransistor TFT through a through hole TH3 that is created in theinterlayer insulating film IN2, the passivation film PAS2 (color filterCF) and the passivation film PAS1 in advance at the end on the thin filmtransistor TFT side. The above described opening OP for exposing theperiphery of the above described through hole TH3 is created in thecounter electrode CT formed on the passivation film PAS 2 (color filterCF), and this opening OP prevents the pixel electrode PX fromelectrically connecting to the counter electrode CT.

Here, in the above described through hole TH3 created in the passivationfilm PAS2 (color filter CF), as shown in FIG. 7, the angle θ2 of theside wall surface relative to the surface of the substrate (the angle θ2of the taper of the contact hole TH3) is set to a value of 45° or moreand 90° or less. Thus, the angle θ2 of the taper of the contact hole TH3is set relatively wide (steep), and the diameter of the contact hole TH3can be made small. Accordingly, the aperture ratio of the pixels can beincreased. Meanwhile, as shown in FIG. 8, in the color filteroverlapping portions which correspond to the sides of the passivationfilm PAS2 (color filter CF), the angle θ1 of the side wall surfacerelative to the substrate (the angle θ1 of the taper in the color filteroverlapping portions) is smaller than the angle θ2 of the taper in thecontact hole TH3, and set to a value of 30° or more and 75° or less.That is to say, θ1 and θ2 are set so that θ1<θ2. In this case, the angleθ1 of the taper in the color filter overlapping portions is setrelatively low (gentle), so that the width of the color filteroverlapping portions (amount of color filter overlap) and the height inthe color filter overlapping portions (difference in thickness betweencolor filters and overlapping portions) are smaller. When the amount ofcolor filter overlap in the color filter overlapping portions is small,the aperture ratio of the pixels is higher. In order to make theaperture ratio of the pixels high, the amount of color filter overlap iswithin a range of 1 μm to 7 μm. In the embodiment in FIG. 8, the widthof the drain lines DL is 3 μm. The drain lines DL are metal wires and donot allow light to transmit. Therefore, the amount of color filteroverlap can be adjusted to the width of the drain lines DL, so that theaperture ratio of the pixels is higher.

In addition, an alignment film is formed on the interlayer insulatingfilm IN2. When the difference in thickness between the color filters andthe overlapping portions is large, the alignment film is affected. Whenthe difference in thickness between the color filters and theoverlapping portions is small in the color filter overlapping portions,the alignment film is highly reliable. In order to suppress disturbancein the alignment film, the difference has to be 1.0 μm or less.

When the angle θ1 of the taper in the color filter overlapping portionsis set to a value within the above described range, the amount of colorfilter overlap is within a range of 1 μm to 7 μm and the difference inthickness between the color filters and the overlapping portions is 1.0or less.

Here, though not shown in FIGS. 7 and 8, the alignment film is formed onthe interlayer insulating film IN2 so as to cover the pixel electrodesPX, and this alignment film makes direct contact with the liquidcrystal, so that the initial alignment of the liquid crystal moleculescan be determined. As described above, the color filters CF are formedso that the difference in thickness between the color filters and theoverlapping portions is small in the color filter overlapping portions,and therefore, a highly reliable alignment film can be formed.

<Manufacturing Method>

Next, the manufacturing method for the above described color filters CFis described. Here, prior to the description of the manufacturing methodfor the color filters CF, certain relationships between exposure tolight when color filters CF are formed in accordance with aphotolithographic technology, the density of the pigment contained inthe color filters CF, the angle of the taper at the end of the colorfilters CF, the difference in thickness between the color filters CF andthe color filter overlapping portions where the tapers overlap, and theamount of color filter overlap are described.

First, the x axis is the amount of exposure to light (mJ/cm2) and the yaxis is the angle of the taper (°) in the graph of FIG. 9, which showsthe angle of the taper relative to the amount o exposure to light fordifferent densities of the pigment contained in the color filter CF. Thedensity of the pigment is set to 60%, 35% and 10%. Though the adhesionof the color filters to the substrate SUB1 is known to be great when theamount of exposure to light is great, FIG. 9 shows that the greater theamount of exposure to light is, the greater the angle of the taper is.Thus, it is clear that the angle of the taper can be controlled to adesired value in color filters CF having high adhesion to the substrateSUB1 when halftone exposure to light is carried out in the taperedportions. In addition, the x axis is the angle of the taper (°) and they axis is the difference in thickness between the color filters and theoverlapping portions (μm) in the graph of FIG. 10, which shows thedifference in thickness between the color filters and their overlappingportions relative to the angle of the taper for different amounts ofoverlap between adjacent color filters CF. As is clear from FIG. 10, thedifference in thickness between color filters and their overlappingportions can be adjusted to a desired value by controlling the angle ofthe taper of the color filters CF.

FIG. 5 shows an example of a color filter CF(R) from among the colorfilters CF in FIGS. 6, 7 and 8. The structure described below can beused for the color filters CF(B) and CF(G). The color filters CF(R) areformed of a resin material containing a pigment in accordance withphotolithographic technology, as described above, so as to cover all ofthe pixels aligned in the direction y in the figure, for example.

The left side of the color filter CF(R) overlaps the color filterdirectly to the left (not shown) in the color filter overlapping portionPL (indicated by PL1 in the figure), while the right side of the colorfilter CF(R) overlaps the color filter directly to the right (not shown)in the color filter overlapping portion PL (indicated by PLr in thefigure). Here, the width R of the color filter CF(R) is referred to aspixel size. In addition, halftone exposure to light may in some cases becarried out in an area covering the width w1 on the side of the colorfilter CF(R), and w1 is referred to as size of halftone processing inthe color filter overlapping portions. Here, though in the figure thewidth of the color overlapping portions PL and the size of halftoneprocessing w1 in the color filter overlapping portions are the same, thetwo may be different, but the width of the above described coloroverlapping portions PL is synonymous to the amount of color filteroverlap.

In addition, a square through hole TH3 is created in the center portionof the color filter CF(R), in the lower half in the figure. Here, thelength L of the sides of the through hole TH3 is referred to as diameterfor processing a contact hole. In addition, halftone exposure to lightmay in some cases be carried out over an area covering the width w2inside the through hole TH3, and w2 is referred to as size of halftoneprocessing in the contact hole.

Table 2 shows the density of the pigment, the amount of exposure tolight in the photolithographic technology, the size of halftoneprocessing in the contact hole, the angle θ2 of the taper in the contacthole for different sizes of halftone processing in the color filteroverlapping portions (tenth to twenty-eighth embodiments), as well asthe angle θ1 of the taper in the color filter overlapping portions.

TABLE 2 Difference Size of Size of halftone Angle θ 1 Amount inthickness Amount of Diameter for halftone Angle θ 2 processing in oftaper in of color between color Density of exposure processingprocessing in of taper in pixel color filter color filter filter filtersand Pigment to light contact hole contact holes contact holes sizeoverlapping overlapping overlap overlapping (%) mJ/cm² (μm) (μm) (°)(μm) portions (μm) portions (°) (μm) portions (μm) Comparative 60 200 90 120 25 5 60 3 0.6 Example 2 Tenth 1 90 Embodiment Eleventh 2 80Embodiment Twelfth 3 70 Embodiment Comparative 35 175 7 0 95 40 0.5Example 3 Thirteenth 1 70 Embodiment Fourteenth 2 60 EmbodimentFifteenth 3 50 Embodiment Comparative 10 200 5 0 95 30 0.4 Example 4Sixteenth 1 55 Embodiment Seventeenth 2 45 Embodiment Comparative 60 1257 0 90 50 0 90 5 1.2 Example 5 Eighteenth 1 75 5 1.0 EmbodimentNineteenth 3 65 3 0.6 Embodiment Twentieth 5 55 1 0.3 EmbodimentComparative 35 140 80 37.5 0 80 5 1.1 Example 6 Twenty-first 1 70 3 0.7Embodiment Twenty-second 3 60 5 0.8 Embodiment Twenty-third 5 50 7 1.0Embodiment Twenty-fourth 10 120 55 25 1 50 3 0.6 Embodiment Twenty-fifth3 40 3 0.5 Embodiment Twenty-sixth 5 30 3 0.4 Embodiment Twenty-seventh60 100 7 0 78 25 3 40 3 0.5 Embodiment Twenty-eighth 35 200 9 2 70 50 560 1 0.4 Embodiment

First, Table 2 shows the size of halftone processing for differentsettings for the contact hole and a constant amount of color filteroverlap in the tenth to seventeenth embodiments. In the tenth to twelfthembodiments, the density of the pigment in the color filters CF (%), theamount of exposure to light (mJ/cm²) and the diameter for processing thecontact holes (μm) are 60%, 200 mJ/cm² and 9 μm, respectively. When thesize of halftone processing in the contact holes is 1 μm, as in thetenth embodiment, the angle of the taper in the contact holes is 90°. Inaddition, when the size of halftone processing in the contact holes is 2μm, as in the eleventh embodiment, the angle of the taper in the contactholes is 80°. In addition, when the size of halftone processing in thecontact holes is 3 μm, as in the twelfth embodiment, the angle of thetaper in the contact holes is 70°. In contrast, when the size ofhalftone processing in the contact holes is 0 μm, as in ComparativeExample 2, the angle of the taper in the contact holes is 120° and thetaper is reversed. It is necessary for the pixel electrodes PX to beelectrically connected to the source electrodes ST of the thin filmtransistors TFT through the through holes TH3. When the side walls ofthe through howls TH3 are in reverse taper, it is difficult toelectrically connect the pixel electrodes PX and the source electrodes.In order to prevent disconnection between the pixel electrodes PX andthe source electrodes, the side wall surfaces of the contact holes TH3are created so that the angle θ2 is 90° or less. Preferably the angle θ2of the side wall surfaces of the contact holes TH3 is 45°≦θ2≦90°.

In the thirteenth to fifteenth embodiments, the density of the pigmentin the color filters CF (%), the amount of exposure to light (mJ/cm2)and the diameter for processing the contact holes (μm) are 35%, 175mJ/cm2 and 7 μm, respectively. When the size of halftone processing inthe contact holes is 1 μm, as in the thirteenth embodiment, the angle ofthe taper in the contact holes is 70°. In addition, when the size ofhalftone processing in the contact holes is 2 μm, as in the fourteenthembodiment, the angle of the taper in the contact holes is 60°. Inaddition, when the size of halftone processing in the contact holes is 3μm, as in the fifteenth embodiment, the angle of the taper in thecontact holes is 50°. In contrast, when the size of halftone processingin the contact holes is 0 μm, as in the Comparative Example 3, the angleof the taper in the contact holes is 95 and the taper is reversed.

In the sixteenth and seventeenth embodiments, the density of the pigmentof the color filters CF (%), the amount of exposure to light (mJ/cm2)and the diameter for processing the contact holes (μm) are 10%, 200mJ/cm2 and 5 μm, respectively. When the size of halftone processing inthe contact holes is 1 μm, as in the sixteenth embodiment, the angle ofthe taper in the contact holes is 55°. In addition, when the size ofhalftone processing in the contact holes is 2 μm, as in the seventeenthembodiment, the angle of the taper in the contact holes is 45°. Incontrast, when the size of halftone processing in the contact holes is 0μm, as in Comparative Example 4, the angle of the taper in the contactholes is 95° and the taper is reversed.

Next, Table 2 shows the size of halftone processing for differentsettings for the color filter overlapping portions and a constantdiameter for processing the contact holes and size of halftoneprocessing in the contact holes in the eighteenth to twenty-sixthembodiments.

In the eighteenth to twentieth embodiments, the density of the pigmentof the color filters CF (%), the amount of exposure to light (mJ/cm2)and the pixel size (μm) are 60%, 125 mJ/cm2 and 50 μm, respectively.When the size of halftone processing in the color filter overlappingportions is 1 μm, as in the eighteenth embodiment, the angle of thetaper in the color filter overlapping portions is 75°, the amount ofcolor filter overlap is 5 μm, and the difference in thickness betweencolor filters and overlapping portions is 1.0 μm. When the size ofhalftone processing in the color filter overlapping portions is 3 μm, asin the nineteenth embodiment, the angle of the taper in the color filteroverlapping portions is 65°, the amount of color filter overlap is 3 μm,and the difference in thickness between color filters and overlappingportions is 0.6 μm. When the size of halftone processing in the colorfilter overlapping portions is 5 μm, as in the twentieth embodiment, theangle of the taper in the color filter overlapping portions is 55°, theamount of color filter overlap is 1 μm, and the difference in thicknessbetween color filters and overlapping portions is 0.3 μm. In contrast,when the size of halftone processing in the color filter overlappingportions is 0 μm, as in Comparative Example 5, the angle of the taper inthe color filter overlapping portions is 90°, the amount of color filteroverlap is 5 μm, and the difference in thickness between color filtersand overlapping portions is 1.2 μm.

In the twenty-first to twenty-third embodiments, the density of thepigment of the color filters CF (%), the amount of exposure to light(mJ/cm2) and the pixel size (μm) are 35%, 140 mJ/cm2 and 37.5 μm,respectively. When the size of halftone processing in the color filteroverlapping portions is 1 μm, as in the twenty-first embodiment, theangle of the taper in the color filter overlapping portions is 70°, theamount of color filter overlap is 3 μm, and the difference in thicknessbetween color filters and overlapping portions is 0.7 μm. When the sizeof halftone processing in the color filter overlapping portions is 3 μm,as in the twenty-second embodiment, the angle of the taper in the colorfilter overlapping portions is 60°, the amount of color filter overlapis 5 μm, and the difference in thickness between color filters andoverlapping portions is 0.8 μm. When the size of halftone processing inthe color filter overlapping portions is 5 μm, as in the twenty-thirdembodiment, the angle of the taper in the color filter overlappingportions is 50°, the amount of color filter overlap is 7 μm, and thedifference in thickness between color filters and overlapping portionsis 1.0 μm. In contrast, when the size of halftone processing in thecolor filter overlapping portions is 0 μm, as in Comparative Example 6,the angle of the taper in the color filter overlapping portions is 80°,the amount of color filter overlap is 5 μm, and the difference inthickness between color filters and overlapping portions is 1.1 μm.

In the twenty-fourth to twenty-sixth embodiments, the density of thepigment of the color filters CF (%), the amount of exposure to light(mJ/cm2) and the pixel size (μm) are 10%, 120 mJ/cm2 and 25 μm,respectively. When the size of halftone processing in the color filteroverlapping portions is 1 μm, as in the twenty-fourth embodiment, theangle of the taper in the color filter overlapping portions is 50°, theamount of color filter overlap is 3 μm, and the difference in thicknessbetween color filters and overlapping portions is 0.6 μm. When the sizeof halftone processing in the color filter overlapping portions is 3 μm,as in the twenty-fifth embodiment, the angle of the taper in the colorfilter overlapping portions is 40°, the amount of color filter overlapis 3 μm, and the difference in thickness between color filters andoverlapping portions is 0.5 μm. When the size of halftone processing inthe color filter overlapping portions is 5 μm, as in the twenty-sixthembodiment, the angle of the taper in the color filter overlappingportions is 30°, the amount of color filter overlap is 3 μm, and thedifference in thickness between color filters and overlapping portionsis 0.4 μm.

Furthermore, Table 2 shows the size of halftone processing for creatingcontact holes and forming color filter overlapping portions in thetwenty-seventh and twenty-eighth embodiments. In the twenty-seventhembodiment, the density of the pigment of the color filters CF (%), theamount of exposure to light (mJ/cm2) and the diameter for processingcontact holes (μm) are 60%, 100 mJ/cm2 and 7 μm, respectively. When thesize of halftone processing in the contact holes is 0 μm, the angle ofthe taper in the contact holes is 78°. In addition, when the pixel sizeis 25 μm and the size for halftone processing in the color filteroverlapping portions is 3 μm, the angle of the taper in the color filteroverlapping portions is 40°, the amount of color filter overlapping is 3μm, and the difference between the color filters and their overlappingportions is 0.5 μm. In the twenty-eighth embodiment, the density of thepigment in the color filters CF (%), the amount of exposure to light(mJ/cm2) and the diameter for processing the contact holes (μm) are 35%,200 mJ/cm2 and 9 μm, respectively. When the size of halftone processingin the contact holes is 2 μm, the angle of the taper in the contactholes is 70°. In addition, when the pixel size is 50 μm and the size ofhalftone processing in the color filter overlapping portions is 5 μm,the angle of the taper in the color filter overlapping portions is 60°,the amount of color filter overlap is 1 μm, and the difference inthickness between the color filters and their overlapping portions is0.4 μm.

As is clear from the above description, in the liquid crystal displaydevice and the manufacturing method for the same according to thepresent invention, halftone exposure to light is used, so that the angleof the taper in the contact holes is large and the angle of the taper inthe color filter overlapping portions is small in COA color filters.

Though embodiments of the present invention are described above, thestructures in these embodiments are merely examples, and variousmodifications are possible for the present invention, as long as thetechnological idea is not deviated from. In addition, the structures inthese embodiments may be combined for use, as long as they arecompatible.

What is claimed is:
 1. A liquid crystal display device, comprising apair of substrates positioned so as to face each other and sandwichliquid crystal, wherein gate signal lines made of a light blockingmaterial which run in a first direction and are aligned in a seconddirection which crosses said first direction, and drain signal linesmade of a light blocking material which run in said second direction andare aligned in said first direction, are formed on the surface of one ofthe two substrates, on the liquid crystal side, and thin filmtransistors which are turned on by a scanning signal through a gatesignal line and pixel electrodes to which a video signal is suppliedfrom a drain signal line through a thin film transistor when turned onare provided in pixel regions, pixel regions being defined as regionssurrounded by two adjacent gate signal lines and two adjacent drainsignal lines, wherein: each of said pixel regions is provided with atleast a gate signal line, a drain signal line and a color filter formedin a layer above a thin film transistor, overlapping regions betweenadjacent first color filters and second color filters are provided inregions in which said drain signal lines or said gate signal lines areformed as viewed from the top, each of the first color filters in theoverlapping regions is underlying each of the second color filters inthe overlapping regions, and the angle of the first taper of said firstcolor filters formed in said overlapping regions is set to 45° or moreand 90° or less relative to the surface of said drain signal lines orgate signal lines, the angle of the second taper of said second colorfilters formed in said overlapping regions is set to 45° or more and 90°or less relative to the surface of said first color filters, the angleof the first taper is smaller than the angle of the second taper, andthe width of said signal lines is set to 1 μm or more and 4 μm or less.2. The liquid crystal display device according to claim 1, wherein thefilm thickness of each color filter is set to 1 μm or more and 4 μm orless.
 3. The liquid crystal display device according to claim 1, whereinthe film thickness of each color filter is set to 1 μm or more and 4 μmor less, and the overlapping portions between said first color filtersand said second color filters have a step of 1 μm or less.
 4. The liquidcrystal display device according to claim 1, wherein the end of thefirst taper of said first color filters overlaps with the second taperof said second color filters.
 5. The liquid crystal display deviceaccording to claim 1, wherein the angle of the first taper of said firstcolor filters formed in said overlapping regions is set to 45° or moreand 70° or less relative to the surface of said drain signal lines orgate signal lines, and the angle of the second taper of said secondcolor filters formed in said overlapping regions is set to 45° or moreand 70° or less relative to the surface of said first color filters. 6.The liquid crystal display device according to claim 1, wherein thedensity of the pigment in said color filters is 10% or more and 60% orless.
 7. The liquid crystal display device according to claim 1, whereinthe density of the pigment in said second color filters is lower thanthe density of the pigment in said first color filters.
 8. The liquidcrystal display device according to claim 1, wherein the relativedielectric constant of said color filters is 3.0 or more and 7.0 orless.
 9. The liquid crystal display device according to claim 1, whereinsaid color filters are formed in accordance with a selective etchingmethod by means of photolithographic technology using an aligner orstepper.
 10. A manufacturing method for a liquid crystal display devicecomprising: a pair of substrates provided so as to face each other andsandwich liquid crystal, gate signal lines which run in a firstdirection and are aligned in a second direction which crosses said firstdirection, and drain signal lines which run in said second direction andare aligned in said first direction; thin film transistors driven by ascanning signal from a gate signal line; and color filters formed so asto cover said gate signal lines, said drain signal lines and said thinfilm transistors, and pixel electrodes formed in a layer above thesecolor filters, by comprising: forming said color filters with coloroverlapping portions where adjacent color filters overlap, and at thesame time creating contact holes for electrically connecting said pixelelectrodes to said thin film transistors; and carrying out halftoneexposure to light in the contact hole portions of said color filters,the color overlapping portions, or both, so that the angle of the taperin said color overlapping portion is smaller than the angle of the taperof said contact holes when said color filters are formed in accordancewith photolithographic technology; wherein said color filters have colornon-overlapping portions where adjacent color filters don't overlap;each of the color non-overlapping portions is arranged in an areabetween adjacent color filters and has the contact hole; and a width ofeach of the color overlapping portions is narrower than a width of eachof the color non-overlapping portions.
 11. The manufacturing method fora liquid crystal display device according to claim 10, wherein the angleof the taper in said color overlapping portions in said color filters is30° or more and 75° or less.
 12. The manufacturing method for a liquidcrystal display device according to claim 10, wherein the angle of thetaper in said contact holes in said color filters is 45° or more and 90°or less.
 13. The manufacturing method for a liquid crystal displaydevice according to claim 10, wherein the color filters are formed so asto contain a pigment, and the density of the pigment is 10% or more and60% or less.
 14. The manufacturing method for a liquid crystal displaydevice according to claim 10, wherein the amount of color overlap insaid color overlapping portions in said color filter is 1 μm or more and7 μm or less.
 15. The manufacturing method for a liquid crystal displaydevice according to claim 10, wherein the halftone exposure to light insaid color overlapping portions in said color filters is carried out inan area 1 μm to 5 μm from the end of said color filters.
 16. Themanufacturing method for a liquid crystal display device according toclaim 10, wherein the halftone exposure to light in said contactportions in said color filters is carried out in an area 1 μm to 5 μmfrom the edge of said contact portions.
 17. A liquid crystal displaydevice, comprising: a pair of substrates provided so as to face eachother and sandwich liquid crystal, gate signal lines which run in afirst direction and are aligned in a second direction which crosses saidfirst direction, and drain signal lines which run in said seconddirection and are aligned in said first direction; thin film transistorsdriven by a scanning signal from a gate signal line; and color filtersformed so as to cover said gate signal lines, said drain signal linesand said thin film transistors, and pixel electrodes formed in a layerabove these color filters, wherein: said color filters have coloroverlapping portions where adjacent color filters overlap and contactholes for electrically connecting said pixel electrodes to said thinfilm transistors; and the angle of the taper in said color overlappingportion is smaller than the angle of the taper of said contact holes;said color filters have color non-overlapping portions where adjacentcolor filters don't overlap; each of the color non-overlapping portionsis arranged in an area between adjacent color filters and has thecontact hole; and a width of each of the color overlapping portions isnarrower than a width of each of the color non-overlapping portions. 18.The liquid crystal display device according to claim 17, wherein theangle of the taper in said color overlapping portions in said colorfilters is 30° or more and 75° or less.
 19. The liquid crystal displaydevice according to claim 17, wherein the angle of the taper in saidcontact holes in said color filters is 45° or more and 90° or less. 20.The liquid crystal display device according to claim 17, wherein thecolor filters are formed so as to contain a pigment, and the density ofthe pigment is 10% or more and 60% or less.
 21. The liquid crystaldisplay device according to claim 17, wherein the amount of coloroverlap in said color overlapping portions in said color filter is 1 μmor more and 7 μm or less.